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Casting can no longer produce undefined behavior (UB) #59

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martin-t opened this issue Jul 29, 2020 · 3 comments · Fixed by #61
Closed

Casting can no longer produce undefined behavior (UB) #59

martin-t opened this issue Jul 29, 2020 · 3 comments · Fixed by #61

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@martin-t
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It looks like the 2 issues linked here and in some other places have been resolved and the reference has been updated too.

Should i update the docs?
@yoanlcq
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yoanlcq commented Jul 29, 2020

Updating the docs is a good idea. One thing to consider is that some users may not be using the latest 1.45.0 of Rust, so what I think I'll do right now is change the docs to say "hey, if you're using a version Rust before 1.45.0, then you may encounter UB as described: [insert current doc about UB here]".

Then I guess one day Rust 1.45.0 would be widespread enough that we could completely remove to parts of the doc about UB. I am unsure of when that day will come and how to measure it, but I guess that'll be fine.

yoanlcq added a commit that referenced this issue Jul 29, 2020
@yoanlcq
Update doc about UB in 'as' casts; Mention #59
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@yoanlcq
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yoanlcq commented Jul 29, 2020

That should be fine, let me know if you have any thoughts about this.

@martin-t martin-t mentioned this issue Jul 30, 2020
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@martin-t
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I noticed the text here originally comes from the num-traits crate and opened a PR there. In the process, i noticed the second case (float to float conversion) probably never was UB and the second example might be removed. Might wanna keep an eye on that PR to keep the docs in sync.

bors bot added a commit to rust-num/num-traits that referenced this issue Aug 24, 2020
@bors @martin-t
Merge #184
3196236 
184: Update AsPrimitive Safety docs for rust 1.45 r=cuviper a=martin-t

Fixes #174

The safety section should not be removed entirely since people might be using older compilers (as was pointed out to me in a [related issue](yoanlcq/vek#59) in the vek crate).

However, [this](rust-lang/rust#15536 (comment)) and followup comments indicate that the second case (float to float) was never UB in the first place - should the second example be removed?

Co-authored-by: Martin Taibr <taibr.martin@gmail.com>
@martin-t martin-t mentioned this issue Nov 23, 2020
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Remove example that was never UB martin-t/vek
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@martin-t @yoanlcq